Radiosonde



- 1, 1959 G. R. MADLAND ETAL 2,915,624

RADIOSONDE Filed Aug. 21, 1956 2,915,624' Patented Dec. 1, 1959 RADIOSONDE Glen R. Madland, Elmhurst, and Raymond G. Worobey, Chicago, Ill., assignors to Motorola, Inc., Chicago, Ill., a corporation of Illinois Application August 21, 1956, Serial No. 605,349 Claims. (Cl. Z50-17) The invention` relates to meteorological apparatus, known as radiosondes, which apparatus is carried aloft by a balloon or other means and which transmits data such as temperature, humidity, and atmospheric pressure.

Most radiosondes take the form of a high frequency oscillator which is repeatedly interrupted by a relaxation device such as a blocking oscillator. The rate of interruption is determined by the blocking rate of the relaxation device, and this blocking rate may be controlled by varying the value of the resistor in its grid circuit. Various resistors respectively sensitive to ternperature, humidity, etc., are selectively switched or commutated into the blocking oscillator circuit so that an interrupted carrier wave may be transmitted, having an interruption rate indicative of the value of its corresponding atmospheric condition.

In order to operate Such a device, of about 1680 mc. is required. the carrier Vfrequency oscillator used a relatively expensive tube to achieve such a high frequency. Since the radiosonde after being carried aloft is not usually recoverable, it is extremely important to make the apparatus as cheap as possible without impairing its ability to furnish accurately the desired amount of data.

It is, accordingly, an object of the present invention a carrier frequency In the prior art units,

to provide an improved radiosonde which is capable of stable operation at the required high frequency of such apparatus and yet which uses relatively simple component parts and a relatively inexpensive electron discharge device in the high frequency oscillator.

Another object of the invention is to provide such an improved radiosonde which may be adjusted easily and conveniently to precisely the desired transmission frequency.

A further object of the invention is to provide such an improved radiosonde which operates with a minimum power output to provide sui'licient intensity and thereby conserve the available power until such time as it is required.

A feature of the invention is the provision in a radiosonde of a high frequency oscillator which uses spaced metallic strips as plate-grid transmission lines, and `in which the electron discharge tube of the oscillator plugs directly into integral resilient sockets formed directly into the ends of the strips and without the use of tube sockets.

Another feature of the invention is the provision of a tuning means for the above mentioned transmission line which takes the form of respective insulating strips interposed between the metallic strips and movable therein to adjust the distributed capacity of the lines.

Yet another feature is the provision of such a tuning means in which a rotatable drive for at least one of the insulation strips is provided which extends across the strip at right angles to the direction of movement thereof for convenient adjustment from the side of the radiosonde. p

A further feature of the invention is the provision of a pressure sensitive resistor in the grid circuit of the high frequency oscillator, which resistor increases the gain of the discharge tube therein as the height of the radiosonde increases, so that increased signal intensity is provided as the distance of transmission increases.

. This holds the power consumption at any time to just what is necessary to provide sufficient intensity to the transmitted signals, and results in greater available power at the maximum distance of transmission.

The above and other features of the invention which are believed to be new are set forth with particularity in the appended claims. The invention itself, however, together with further objects and advantages thereof, may best be understood by reference to the following description when taken in conjunction with the accompanying drawing in which:

Fig. 1 is an assembled view of the radiosonde of the present invention attached to its battery casing;

Fig. 2 is a side view of the unit with the casing removed;

Fig. 3 is also a side view of the unit taken from the opposite side to that of Fig. 2;

Fig. 4 is a sectional view, partly schematic, of the radiosonde unit; and

Fig. 5 is a schematic diagram illustrating one feature of the invention.

The invention provides in a radiosonde, a metallic plate-like member forming a plane of reference potential, with a rst metallic strip spaced from one side of the plate and essentially parallel thereto and a second metallic strip spaced from the opposite side of the plate and essentially parallel thereto. A first insulating strip is slidable between the first metallic strip and the plate to tune the transmission line formed thereby, and asecond insulating strip is slidable between the second metallic strip and the plate to tune the transmission line formed by these latter components. An electron discharge device is provided which includes a cathode, a grid, and a plate, and which has respective protruding pins connected to these electrodes. The lirst metallic strip has at least one integral longitudinal resilient eyelet formed therein for receiving the grid pin of the discharge device, and the second metallic strip has a similar eyelet formed therein for receiving the plate pin of the device. The cathode pin is connected to the plate of reference potential, and the grid pin is connected to the reference by a resistor.

The radiosonde shown in Fig. 1 includes an outer casing 10 of generally cylindrical shape, and this casing snaps into a housing 11 containing the battery for the unit. The assembly 10, 11 is adapted to be carried by a balloon, projectile, or by any other known means.

The radiosonde itself includes a flat insulating chassis 12 which may be, for example, a phenolic resin, such as Bakelite, and which extends longitudinally of casing 10. A cone shaped member 13 is secured to one end of the insulating chassis 12 and supports an antenna 14 at its apex. Both the cone 13 and antenna 14 are protected by the end portion of casing 10 (Fig. l) which has a somewhat similar configuration. The assembly 12, 13, and 14 is retained in the casing 10 by means of a disclike member 15 extending across the bottom of the casing and which is held in place by any suitable means.

The insulating chassis 12 has a printed circuit 16 formed on one side thereof, and this side also supports components such as electron tube 17, coil 18, resistors 19, and other elements that make up the blocking oscillator which is included in the apparatus. Since this oscillator per se forms no part of the present invention and may take any well known form, a further description of the blocking oscillator is deemed to be unnecessary herein. It is believed sufficient to state that, as previously noted,

Thehighfrequency oscillator is mounted on the other.` side of the insulating chassis l2, andit includes a lower metallic shield (Fig. 4) of the` rectangular channell configuration and which is secured to the chassis 12- by screws such as 2l` and 22. A metallic plate 23 is mounted onthe shield Ztl, and both the plate and shield are establishedat a. reference potential, such as ground. A metallic strip 24fis held in spaced 'parallel` relation with the underside of plate 2 3 by an insulating rivet-25= which may be composed, for example, of Tefion which is a polyuoride plastic. An insulating strip 26 is slidably disposed between strip 24 and the plate 23. Strip 26 may be a thermosetting plastic, such as a copolymer of styrene. The longitudinal positionl of insulatingA strip 26 may be adjusted by the spring loaded screw 27.

The high frequency oscillator includes an electron discharge tube 28. The grid pins from tube 23 are plugged directly into corresponding resilient integral longitudinal eyelets 29 formed in the end of strip 24 and which will be referred to herein as lances The cathode pin of device 28.is connected to the plate 23 by any suitable means. The strip 24 and plate 23 form a grid-ground transmission line, and this line may be tuned by the longitudinal adjustment of insulating strip 26 by screw 27. This insulating strip effectively adds distributed capacity to a portion of the line and changes its characteristic impedance. The line is shielded by the metallic shield 20 referred to previously herein. The grid pin of the tube 23 is connected to the plate 23 by a resistor 30,

which resistor may bepressure sensitive so that the gainof the. .tube varies lwith pressure. This gain variation causes the intensityof the output of the high frequency oscillator to increase as the height of the radiosonde increases, so that only the necessary power level at any time is established. This tends to a greater power level at maximum distance of transmission.

A second metallic strip 31 is supported in spaced parallel relation with the other side of plate 23 by an insulating rivet 32, and this second strip has lances 33 formed in its end to receive the plate pins of tube 28. An insulating strip 34 is slidable between metallic strip 31 and plate 23, and the insulating strip has a diagonal slot 35 formed therein. A second rectangular channel shaped shield 36 is secured to plate 23 and surrounds the strip 31. A screw 37 is rotatably mounted in the sides of shield 36, and the screw extends across strip 34. The shield 36 is shown in section in Fig. 3 to show this construction. A dog 38 is threaded to screw 37 and extends into slot 35. Therefore, rotation of screw 37 produces longitudinal motion to the insulating strip 34 between strip 31 and plate 23 in a direction perpendicular to the longitudinal axis of screw 37. Screw 37 has a slotted head 39 which is adapted to receive a screw driver or other suitable adjusting tool through the hole 40 in casing ttl (Fig. l).

Metallic strip 31 and plate 23 form a transmission line between the plate of tube 2S and ground. This line is tuned by the insulating strip 34 when screw 37 is tuned, because this strip adds distributed capacity to a portion. of the line and changes its characteristic impedance.

The plate of tube 2S is connected to the positive terminal of B-lof the battery power supply in casing 11 through choke coil 41. Output power is derived from loop 42 which is spaced from strip 31 and which is connected to antenna 14 through a shielded cable 43. This loop is both inductively and capacitively coupled to the strip 31.

The tube 28 is connected as a tuned-plate tuned-grid oscillator, with the tuned circuits being formed by the open-circuit, half-wave transmission lines 31, 23 and 24, 23. Each line actually extends into the tube with the corresponding tube element and its lead and pin forming a portion of the line. For example, metallic plate 3l, the plate pins and leads within tube 2S cooperate to form the transmission line, and when standing waves appear on this line they extend into the tube itself. This also applies to the line including thestrip 24, the grid pins and the grid leads within tube 2S.

To consider the operation of the lines, reference is made to Fig. 5 which illustrates the circuit between the plate and cathode of tube 28; Capacitor 45 represents the plate to grid capacitance of the tube, inductor 46 represents the inductance of the plate lead, pin, etc., and inductor 47 represents the inductance of the cathode lead, pin, etc. At the high frequency involved, the inductances are substantial and when no external inductor is used, the frequency may be below the desired frequency. This frequency of oscillation producedwhen a high frequene short circuit is `placed across theftuberelements is` known as the natural frequency of` the tube. In the circuit shown, the transmission line23, Slis connected to the plate and cathode pins. The length of theA line is less than a quarter wave lengthmaking it look capacitive. This reduces the phase shift through the inductors 45 and 47' formed by the tube structure to permit the tube to oscillate at a frequency above its natural frequency. This arrangement enables theV extremely high frequency of the order of 16S() megacycles to be obtained for the radiosonde, despite the fact that tube 2S can be a relatively inexpensive tube not normally capable of generating such a high frequency.

The oscillator is tuned by the tuning means including screw 27 and by tuning means including screw 37. Both of these tuning means, ofcourse, may be the same and may be like the one of screw 27 or the one of screw The tuning means of screw 37 is preferred for at least one of the tuning adjustments since it enables Vtuning to be made from the side of casing liti when the casi:` in place on housing il. With tuning means such as the one of screw 27, the casing l@ must first be removed from the housing lill. Tuning means of screw 37 allows a nal precise frequency adjustment to be made when the unit is fully assembled.

The invention provides, therefore, a radiosonde which includes a high frequency oscillator in which feedback is obtained through the interelectrode capacity of tube 28 by electrically positioning the cathode of the tube between the grid and plate. As previously noted, the tube oscillates at a frequency above its own natural frequency at, for example, 1680 megacycles. The tuned circuits. as previously mentioned, are open-circuit, half-wave lines providing a tuned-plate tuned-grid type oscillator. The oscillator is completely shielded by shields 20 and 36, and these reduce radiation losses and improve the power output.

The radiosonde of the invention, therefore, is relatively inexpensive in itsV construction and may use a relatively inexpensive tube. The unit may be conveniently tuned in a manner described herein, and a precise final frequency adjustment may be made through the convenient aperture 40 in the sidevof casing l. Moreover, and as noted herein, resistor 30 may be made pressure sensitive for power economy so that increased power is used only when it is needed.

We claim:

1. In a high frequency translating system which includes an electron discharge tube having plate and grid electrodes with connecting pins connected thereto and extending from one end of the tube, the combination of a transmission` line including first and Asecond spaced metallic members, means for supporting said pins in direct electrical contact with said first and second metallic members, so that said pins extend essentially parallel to the longitudinal axis of said transmission line, and an insulating strip interposed between said metallic members and movable with respect thereto to change the distributed capacity between said members and the characteristic impedance of said transmission line.

2. In a high frequency translating system which includes an electron discharge tube having a plurality of connecting pins extending from one end thereof, the combination of a pair of spaced metallic strips forming a transmission line, a longitudinal resilient eyelet formed in each of said strips for receiving two of the connecting pins of the discharge tube, so that the pin received by said eyelet extends essentially parallel to the plane of the strip in which said eyelet is formed, and an insulating strip interposed between said metallic strips and movable longitudinally thereof to change the distributed capacity of said strips and the characteristic impedance of said line.

3. In a radiosonde unit, a high frequency oscillator which includes an electron discharge tube having a cathode, a control grid and a plate, and having respective pins connected thereto and protruding from end of the tube; the combination of a metallic plate forming a plane of reference potential; a rst metallic strip spaced from one side of said plate and essentially parallel thereto; a second metallic strip spaced from the opposite side of said plate and essentially parallel thereto; means for connecting the grid pin of -said discharge tube to said first metallic strip with the grid pin extending essentially `,parallel to the longitudinal axis of said first metallic strip, means for connecting the plate pin of said discharge tube to said second metallic strip with the plate pin extending essentially parallel to the longitudinal axis of said second strip; means for connecting the cathode pin of the discharge tube to a point at the reference potential; resistor means lfor connecting said grid pin to a point at the reference potential; and means for connecting said plate pin to a source of positive unidirectional potential. v

4. In the unit dened in claim 3, a first insulating strip interposed between said plate and said trst metallic strip and movable longitudinally thereof, and a second insulating strip interposed between said plate and said second metallic strip and movable longitudinally thereof.

5. In the unit defined in claim 3, at least one insulating strip interposed between said plate and at least one of said metallic strips and having a diagonal slot therein, a screw extending transversely of said4 metallic strips across said insulating strip, and a dog threaded to said screw and extending into said slot, so that rotation of said screw produces rectilinear movement of said insulating strip in a direction perpendicular to the longitudinal axis of said screw.

6. In the unit defined in claim 3, said resistor means connecting said grid pin to a point of the reference potential being pressure-sensitive to control the gain of the discharge tube in accordance with the value of the ambient pressure.

7. In the unit deiined in claim 3, an antenna, and a coupling loop connected to said antenna and inductively and capacitively coupled to said second metallic strip.

8. In a radiosonde unit, a metallic plate forming e A plane of reference potential; a rst metallic strip spaced from one side of said plate and essentially parallel thereto; a second metallic strip spaced from the opposite side of said plate and essentially parallel thereto; a rst insulating strip interposed between said first metallic strip and said plate and slidable therebetween to tune the transmission line formed thereby; a second insulating strip interposed between said second metallic strip and said plate and slidable therebetween to tune the transmission line formed thereby; an electron discharge device including a cathode, a grid and a plate, and having respective pins connected thereto; said rst metallic strip having at least one lance formed therein for receiving the grid pin of said device, and said second metallic strip having at least one lance formed therein for receiving the plate pin of said device; means for connecting the cathode pin to a point of the reference potential; and resistor means for connecting said grid pin to said point of reference potential.

9. In a high frequency oscillator including an electron discharge tube, having a plurality of connecting pins extending from one end thereof, and which oscillator operates at a frequency above the natural frequency of the tube, the combination of a pair of spaced metallic strips forming a transmission line, means formed in said metallic strips at one end of the transmission line for receiving two of the connecting pins of the discharge tube for thereby coupling the tube to the transmission line, and an insulating strip interposed between said metallic strips to provide a capacitive impedance which effectively tunes the oscillator above its natural frequency, said insulating strip being movable longitudinally of said metallic strips to change the distributed capacity of said line and the characteristic impedance thereof.

10. In a high frequency translating system which includes an electron discharge tube having a plurality of connecting pins extending from one end thereof, the combination of a pair of spaced metallic strips forming a transmission line, at least one longitudinal resilient eyelet formed in at least one of the strips for receiving one of the connecting pins of the discharge tube, so that the pin received by said eyelet extends essentially parallel to the plane of the strip in which said eyelet is formed, an insulating strip having a portion interposed between said metallic strips, said insulating strip being mounted for movement along said metallic strip and having a diagonal slot therein, a screw extending across said insulating strip in a direction transverse to said metallic strips, and a dog threaded to said screw and extending into said slot, so that rotation of said screw produces rectilinear movement of said insulating strip in a direction perpendicular to the longitudinal axis of said screw.

References Cited in the le of this patent UNITED STATES PATENTS 1,960,058 Lynn May 22. 1934 2,192,711 Lindenblad Mar. 5, 1940 2,297,266 Vieweger Sept. 29, 1942 2,423,836 Lake et al. July 15, 1947 2,717,362 Press Sept. 6, 1955 2,729,801 Hesse Jan. 3, 1956 2,774,045 Wilcox Dec. 11, 1956 

